Abstract: Based on the station of national, regional station data and NCEP reanalysis data, the two process of heavy precipitation in Hunan on July 19 （0719） and September 4 （0904） under the control of subtropical high were comparatively analyzed. The results show： ①The two process subtropical highs were relatively strong, but their positions were quite different. The main body of “0719” was easterly, while the main body of “0904” was westerly. 925 hPa shear had a good indicating significance for heavy precipitation areas; ② The middle and lower layers of the precipitation area were convective unstable stratification, and 700~500 hPa was neutral stratification, which was conducive to the occurrence and development of precipitation. ③ It is found that the water vapor sources in the two processes were different by the air parcel tracking method. Water vapor mainly came from the western Pacific region in “0719” process, and came from the Indian Ocean region in the process of “0904”. ④ In terms of quantities, the energy of water vapor was vertically divided into unstable stratification of upper dry cold and lower wet warm wet in the “0719” process. In addition, the process vertical rose motion, convergence and divergence, and relative vorticity configuration were shallow, mainly concentrated in the middle and low layers. In the “0904”process, the wet layer was thick in the vertical direction. Influenced by cold air, there was an obvious zone, on the one hand, convergence rose with the warm current rendezvous, lifting up on the other hand, to reinforce upward movement, trigger instability energy, and process of vertical ascending motion area extended upward height higher than the “0719”, low-level convergence layer deep, relative vorticity upload more, corresponding to the greater the rainfall intensity.

Key words: subtropical high, heavy rain, water vapor, Hunan province